Myasthenia gravis (MG) is a chronic autoimmune disorder that occurs when the immune system malfunctions, causing the voluntary (skeletal) muscles to become weak. In Latin, myasthenia gravis literally means "grave muscle weakness."
Myasthenia gravis is classified as an autoimmune disorder because the body's immune system, which normally fights against disease and infection, mistakenly attacks the receptors in the body that allow the nerves and muscles to communicate with one another. The cause for this abnormal response is unknown.
Any voluntary muscle may be affected, but the eye muscles, face muscles, and muscles that control breathing and limb movement are most likely to be affected. Most people experience periods of generalized weakness from time to time. Symptoms generally worsen with physical activity and improve with rest.
Although myasthenia gravis can develop at any age, it is most common in women younger than 40 or older than 70 and in men older than 50 years of age. Symptoms may develop suddenly or gradually over time.
It is estimated that myasthenia gravis affects 0.5-14.2 out of 100,000 people in the United States.
In the past, untreated myasthenia gravis led to death in 30-70% of cases. Today, however, patients have normal or near-normal life expectancies. Although there is still no cure for myasthenia gravis, treatment is available to help manage symptoms. The most common causes of death among patients with myasthenia gravis are respiratory failure (when the muscles that control breathing are too weak to function properly), aspiration (the inhalation of food or drink into the lungs) due to an absent or weakened gag reflex, pneumonia, and falls. Also, some of the medications, such as corticosteroids and immunosuppressants, may cause serious side effects, including an increased risk of infections. This is because these medications help alleviate symptoms by reducing the body's immune response.
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ocular myasthenia gravis, plasmapheresis, single-fiber electromyography, skeletal muscle disorder, thymectomy, thymus gland.